The mission of the Mouse Mutant Resource (MMR) at TJL is to provide a continuing source of new spontaneous mutations for biomedical and biological research. Spontaneous mutations in the mouse are a major source of models for human disorders and have the advantage over genetically engineered mutations in that they are first recognized by producing relevant phenotypes and do not require prior knowledge of the underlying genes. The specific objectives of the MMR program are to: (1) discover new spontaneous mutations in the mouse; (2) characterize the new mutants genetically, phenotypically, and pathologically; (3) establish the new mutations in strains suitable for further analysis; (4) preserve the mutations as frozen embryos or gametes to assure their continued availability and as DNA for future molecular analysis; (5) provide mutant mice and controls to other investigators; and (6) provide information about the mutant mice to others. The new mutations are discovered from among phenotypic deviants appearing in TJL large breeding colonies. They are characterized genetically by determining the mode of inheritance, testing for allelism with known mutations that produce a similar phenotype, and determining the chromosomal location. Each new mutant is characterized phenotypically by observing its growth, viability, fertility, life span, and behavior, and by defining its anatomical, histopathological, and physiological abnormalities. For selected mutants whose phenotype resembles that of an important human disease, the investigators will do further genetic and molecular analysis to identify the mutant gene. The investigators do more in depth analysis on mutants with phenotypes for which a member of the group or a collaborator has specific expertise. The MMR team has expertise in hearing, vision, bone biology, reproduction, and neuropathology. All new mutants with potential for biomedical research will be maintained, preserved as frozen embryos and DNA, and described in the open literature and/or on the MMR and TJL Websites. The overall purpose of the MMR is to make new mutant models available to other investigators for biomedical research.